This proposal is for a study of the natural history of a heroin epidemic which occurred among a population of primarily White, middle and working class high school students and recent graduates. The research design, which should produce a sample of from 475 to 500 respondents, will include interviews with the total population of heroin addicts, all those who experimented with heroin but did not become addicted, all those who were exposed but did not try heroin, and a randomly selected control group of persons from the same high school population. Three research problems will be considered: 1) To describe the pattern of diffusion of a heroin epidemic and to evaluate the applicability of the contagious disease model as an explanation and description of the spread of heroin use: 2) To investigate the social and psychological determinants of levels of heroin use by examining the differences between the addict, experimenter, exposed, and control groups; and 3) To investigate the effects of social and psychological variables on the heroin user's utilization of and success in various treatment modalities.